Custom Anti Roll Bar- Cheap opportunity!
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Kman1600
Member
rockdemon said:
Hi,
Yep tires, or tire, are working hard, the key point is the angle that the wheel has adopted with respect to the road. The wheel is now very much in positive camber, the tire has lost all "purchase" on the road surface and we are in full on understeer, the car is really wanting to go straight on!!! At this point you can floor the throttle in the hope that the rear breaks traction and comes round or back off, let the suspension unwind, the wheel will gain grip and turn in. Heart often says more throttle but really backing off is more often than not the correct call, very unnatural when the clock is ticking!!!
If we stiffen the roll at the front with a heavy ABR the angle the car adopts for the same turning G will be less, thus the positive camber adopted will be less etc…. as discussed before. The down side is that the load on this hard working tire will significantly go up, so the tire might be in a better position but it now has to do more work. The trick is trying to find the point then the positive effect of one condition starts to get overcome by the growing negative effect of the other.
Correcting the front camber requires a geometry change, not easy given the design of the P6’s front suspension.
One obvious question is when does a Modified P6 stop being a P6 and become something else? Part of us wants to keep going with this but part of us feels if we wanted a car that handled like a Mk.2 Escort maybe we should have bought a Mk.2 Escort :roll:
Tim
That's a great write up and it's important to point out the compromises and limitations thanks a lot.
Your picture illustrates why taller profile tires have some tread wrapped over the sides! I'm kind of surprised someone with so many mods is running what looks like standard tyres or can a lower profile work against you at times?
Your picture illustrates why taller profile tires have some tread wrapped over the sides! I'm kind of surprised someone with so many mods is running what looks like standard tyres or can a lower profile work against you at times?
Asking a previously asked question...what did the factory do to mitigate this nasty front end habit when it built the "Rover racer"?
No-one seems to have a definitive answer.
You don't lead factory Porsche's at the Nurburgring by some ungodly amount without sorting that most treacherous frontend!!
No-one seems to have a definitive answer.
You don't lead factory Porsche's at the Nurburgring by some ungodly amount without sorting that most treacherous frontend!!
That's some, erm, interesting things you're front wheel is doing :shock:
It looks like the lower arms are pulling in giving the positive camber at the extremity of the wheels travel, is that right? As it's giving you an issue on cornering, an idea I've had in the past is to build a subframe that locates on the four suspension mounts under the chassis legs, and have new mounts located lower down. Doing that, it may be possible to have longer lower arms fitted, and the geometry designed to help keep the wheels as close to perpendicular to the road under hard cornering. It's only an idea that hasn't gone any further beyond my head, and should in theory be a complete bolt on unit with no bodyshell modifications.
It looks like the lower arms are pulling in giving the positive camber at the extremity of the wheels travel, is that right? As it's giving you an issue on cornering, an idea I've had in the past is to build a subframe that locates on the four suspension mounts under the chassis legs, and have new mounts located lower down. Doing that, it may be possible to have longer lower arms fitted, and the geometry designed to help keep the wheels as close to perpendicular to the road under hard cornering. It's only an idea that hasn't gone any further beyond my head, and should in theory be a complete bolt on unit with no bodyshell modifications.
Demetris
Well-Known Member
Thanks for the information (and the photo!) Tim.
Like everyone else i am also impressed at the outer front wheel attitude during hard cornering, and i am actually wondering how it can have so much positive camber while at almost full bump. If am correct, due to it's design, this suspension will vary a lot between positive camber at rebound and negative camber at bump, the difference being more pronounced on the V8 models due to the shorter lower transverse arms. Could all this movement be due to rubber bushes being compressed?
Also i remember seeing photos of a P6 front suspension with adjustable lower arms. I think that it was in the forum and the rumours were that these were used in the early days of the P6 development to help the engineers fine tune the suspension.
When i got my TC, it had some rather obvious negative camber in the front right wheel. God knows what it must have been through. We managed to correct the alignment by slotting the front lower control bar mounting hole in the base unit, correcting the camber and caster angle at the same time. Perhaps you can try something similar to give some negative camber at the rest position. It is very easy to do, while it is fully reversible if you don't like the results. I understand that adjustable lower arms are the proper way to do it, but this is something significantly more involving.
Like everyone else i am also impressed at the outer front wheel attitude during hard cornering, and i am actually wondering how it can have so much positive camber while at almost full bump. If am correct, due to it's design, this suspension will vary a lot between positive camber at rebound and negative camber at bump, the difference being more pronounced on the V8 models due to the shorter lower transverse arms. Could all this movement be due to rubber bushes being compressed?
Also i remember seeing photos of a P6 front suspension with adjustable lower arms. I think that it was in the forum and the rumours were that these were used in the early days of the P6 development to help the engineers fine tune the suspension.
When i got my TC, it had some rather obvious negative camber in the front right wheel. God knows what it must have been through. We managed to correct the alignment by slotting the front lower control bar mounting hole in the base unit, correcting the camber and caster angle at the same time. Perhaps you can try something similar to give some negative camber at the rest position. It is very easy to do, while it is fully reversible if you don't like the results. I understand that adjustable lower arms are the proper way to do it, but this is something significantly more involving.
Kman1600
Member
Hi,
Car has the “Australian strengthening kit” fitted and the arms are polybushed (maybe good, maybe bad?) so although there has to be some deformation occurring due to the loads involved the front is pretty strong.
In the picture the camber of the wheel relative to the car is not terribly negative but as the car has rolled by quite a few degrees the overall effect is one of positive camber compared to the road.
We could dial in some negative camber at rest but at best we’ll get maybe 1 to 1.5 extra as road tires don’t tend to like much more than that, if however the car rolls by 5 or 6 degrees we are still very positive. The current arrangement fails to recover the camber lost due to the car rolling.
What we need is the suspension to add negative camber as the car rolls, again key is the angle of the wheel to the road not the angle of the wheel to the car.
I’ll try and prompt Gavin to reply to this thread as his understanding of all this is way better than mine, I think he may also have modeled the movement of the front suspension on the computer.
Tim
Car has the “Australian strengthening kit” fitted and the arms are polybushed (maybe good, maybe bad?) so although there has to be some deformation occurring due to the loads involved the front is pretty strong.
In the picture the camber of the wheel relative to the car is not terribly negative but as the car has rolled by quite a few degrees the overall effect is one of positive camber compared to the road.
We could dial in some negative camber at rest but at best we’ll get maybe 1 to 1.5 extra as road tires don’t tend to like much more than that, if however the car rolls by 5 or 6 degrees we are still very positive. The current arrangement fails to recover the camber lost due to the car rolling.
What we need is the suspension to add negative camber as the car rolls, again key is the angle of the wheel to the road not the angle of the wheel to the car.
I’ll try and prompt Gavin to reply to this thread as his understanding of all this is way better than mine, I think he may also have modeled the movement of the front suspension on the computer.
Tim
Attachments
colnerov
Well-Known Member
Hi, I have to state at the outset that I am no expert in this. it looks like some of the
roll of the car is from the tyre tucking under, so as said would a larger diameter wheel
and lower profile tyre help? I was told many years ago that if you make one end of a
car stiffer that end would break away first. So would an ARB at the rear help return the
balance of the car and make under/oversteer more controllable on the throttle? You may
of course be accused of turning it into a drift event. If the inside rear tyre has such a
light grip with the road as the front, surely wouldn't it spin up and lose you time? So can
the roll stiffness of the shell be called into question?
Colin
roll of the car is from the tyre tucking under, so as said would a larger diameter wheel
and lower profile tyre help? I was told many years ago that if you make one end of a
car stiffer that end would break away first. So would an ARB at the rear help return the
balance of the car and make under/oversteer more controllable on the throttle? You may
of course be accused of turning it into a drift event. If the inside rear tyre has such a
light grip with the road as the front, surely wouldn't it spin up and lose you time? So can
the roll stiffness of the shell be called into question?
Colin
vaultsman
Well-Known Member
Kman1600 said:Hi,
Firstly an apology for the length of time it’s taken to get to the point of reviewing this ABR, you make plans and then life gets in the way, anyway it’s on the car and I’ve driven it!!! :shock:
The bar is very well made, radius’s are as large as are practical (good for fatigue resistance) and the fit is excellent. Please note the area of the inner wings of our car have already been opened up slightly to provide clearance around our previous ABR, it appears some cars need this and some don’t, each car is different, in fact each side of each car is different. Bare this in mind if you order one, any extra clearance needed will be small and easily achieve with a little gentle tin bashing/jacking.
On the road the transformation is remarkable; please understand that our car is quite modified now so it is difficult (impossible) to assess this modification in isolation but even compared to our previous 24mm bar this 25.4mm the feel is different, even less roll in the corners. Considering “normal” driving, the bar modernises the feel of the car, you’ll have to decide yourself if that’s a good thing or not? Gone is the rolling nature of the drive, replaced by a much flatter attitude, as I say much more like a modern car would be.
OK so with all of the above said should we all rush out now and order one? Unfortunately a question that sounds as simple as this is surprisingly hard to actually answer. To make an attempt to answer it we need to go through a few things regarding P6 handling and more specifically what the front end is doing. Gavin is way more up on all this stuff than me but this is the just of things, he may come along and elaborate or correct me
Lack of front camber recovery in roll is a big issue with the front suspension geometry, ie when the car rolls the geometry of the front suspension fails to correct for this and the front wheel tucks in under the car and it understeers. This can be seen in the picture below (24mm bar fitted), this eats tires as well as losing loads of time, and it also feels very disconcerting as the bloody thing just won’t turn!!! Increasing the roll stiffness at the front has an obvious effect on this, more stiffness = less roll = less wheel tucking in = better turning = improved times, which is all good
It is extremely hard to know how an otherwise standard car would handle with just this ABR fitted, my gut feel is that it may well be too stiff and all though the car would indeed roll less in the corners overall front end grip might actually be worse.
To most on here all of this is of little consequence as we are talking at the limit handling here, if you fit this bar and drive the car well within its limit all you will notice is the much reduced body roll, which will make it feel more modern. If you want to get the best out of it then fit in along with stronger rear springs, for an otherwise standard car it might be worth considering a mid-stiffness bar. A 22mm bar has been talked about, this might be more appropriate for an otherwise standard car, for reference torsional stiffness percentages over “standard” are listed below (Gav. feel free to check my math :?: ):
22mm bar 145%
24mm bar 188%
25.4mm bar 223%
If you go with stronger rear springs then obviously you can move towards the stiffer bars.
Please understand this is not an exhaustive scientific test, just the best we can do with short run time and limited resources, it would be nice to do back to back trials with various diameter options. The event on the 11th was in fact cancelled due to lack of entries so we are still seeking a full anger event to run on. The above is a review of our observations so far.
On a side note our car went through the MOT this morning without issue, MOT’s here are all state run, no garages, there is no “advisory” process it’s either right and passes or it fails. As most will know our car is no oil painting but it’s right in all the right places :wink: it’s nice to see that the look didn't prejudice the test
All for now, Tim
Many thanks for the comprehensive update, Tim....and I agree with the other subsequent comments - it certainly looks like that tyre's doing some work!
So, in terms of whether this ARB is pursued, it's really down to the owner's whether they wish to alter the P6's inherent roll - to a lesser or greater extent. No change there then, I guess.
I would think the supplier would need a batch of around 15-20 to keep the final price acceptable to us. Also, the batch of bars would all need to be of the same diameter.
Let me know your thoughts if you're interested and I'll keep a tally.
Stan
1396midget
Well-Known Member
I've played with the K-midget's front suspension a lot, and it's bloody complex! no one thing has one effect! I fitted an ARB that was too thick, and it made the car really chattery and horrid over lumpy roads at low speed. I've softened it off a bit now (build an adjustable one - sadly not going to work on the P6) and it's much better. I've got the same problems as Kman in that it's all pretty modified now so working out the effect of one thing is hard.
Has anyone had any luck with controlling transient roll effects with adjustable dampers? It's not the best way to do it but it works well.
Edited to add - Brill photos!
Has anyone had any luck with controlling transient roll effects with adjustable dampers? It's not the best way to do it but it works well.
Edited to add - Brill photos!
1396midget wrote,...
Hi Rob,
I went down that route with my Rover around 25 years ago, fitting Australian made K-Mac springs and Koni adjustable shock absorbers. The springs are quite a bit stiffer than the factory Rover springs, but they are shorter so that the ride height remains within the original spec. Keeping the original anti roll bar, the spring + shock combination makes a noticable improvement with both body roll and dive substantially reduced.
Ron.
Hi Rob,
I went down that route with my Rover around 25 years ago, fitting Australian made K-Mac springs and Koni adjustable shock absorbers. The springs are quite a bit stiffer than the factory Rover springs, but they are shorter so that the ride height remains within the original spec. Keeping the original anti roll bar, the spring + shock combination makes a noticable improvement with both body roll and dive substantially reduced.
Ron.
mikecoombs
Active Member
I have tried the Kmac spring with similar results but when I changed Chassis from my 1971 to 1976 cars (both NZ build) the handling was dramatically better with the standard springs fitted. The part nos for the suspension are the same so I think there must have been a change in the mounting points and I'm reasonably certain that it is about 1/4" + movement of the top links inward - which leaves everything looking the same until you turn a corner and it doesn't understeer. I also found the KMAC Rear sway bar to be next to useless, when I finally figured out how the rear end actually works I realised that it actually doesn't do anything about the role, though it does make the car skittish on dirt. It is simply a bar across the two lower control arms. One other thing I found was that the shock absorbers get very hot after 300 miles or so of high speed rough road driving. I have Konis fitted but want to try asset of Koni Gas shocks. I've tried KYB ones but they don't last long. My view here is that the shock is just too small for hard endurance driving. the car is noticably harder to drive after a long stint.
mikecoombs wrote,...
Hi Mike,
That's interesting that you found the standard springs better on your 76 model. My Rover is a 74, I found the standard springs not to be a patch on the K-Mac items.
I never tried the sway bar for the rear. I recall a conversation that I had, probably during the early to mid 1990's at the Rover Owner's Club annual Display Day. The gent that I was talking to had tried a sway bar on the rear, made it very unstable on dirt, so he pulled it off on the side of the road, if I remember correctly.
Ron.
Hi Mike,
That's interesting that you found the standard springs better on your 76 model. My Rover is a 74, I found the standard springs not to be a patch on the K-Mac items.
I never tried the sway bar for the rear. I recall a conversation that I had, probably during the early to mid 1990's at the Rover Owner's Club annual Display Day. The gent that I was talking to had tried a sway bar on the rear, made it very unstable on dirt, so he pulled it off on the side of the road, if I remember correctly.
Ron.
Geordie Jim
Member
This post seems to have gone off course.
Is anyone collating who would order a 22mm bar?
As Rockdemon said I'm still interested in one.
Jim.
Is anyone collating who would order a 22mm bar?
As Rockdemon said I'm still interested in one.
Jim.
The Rovering Member
Well-Known Member
I think I still would be if the price is right. I'm already stiffer than usual oops & would be interested in the further effects of the bigger bar.
oops & would be interested in the further effects of the bigger bar.
vaultsman
Well-Known Member
Geordie Jim said:
vaultsman said:
Hi Jim,
It does look as if interest in these bars has faded somewhat. Your's and TRM's posts are the only firm restatement of interest since Tim's feedback. (I'd take rockdemon's post as a comment rather than a commitment).
As I said, I'd need around 15-20 hands-up (for a particular diameter) before going back to the supplier for a firm price. I'd expect it to be around the £100 mark for that quantity.
Cheers,
Stan
ghce
Well-Known Member
Life in this thread
I have been talking to the NZ supplier of the 24mm Bar with a view to making a bulk order for supply to those that want one (or 2 or 3 ) and he is amenable to this.
I can not give a price at this stage as I need work out freight costs to the UK (IE) and have been somewhat busy this last month with new wife and other changing goalposts in my life but I know already that the cost will be slightly northward of 100 pounds but this really is freight dependent.
I will make a more concrete proposal later on when I get some idea of the freight and the logistics at the UK delivery end.
Graeme
I have been talking to the NZ supplier of the 24mm Bar with a view to making a bulk order for supply to those that want one (or 2 or 3 ) and he is amenable to this.
I can not give a price at this stage as I need work out freight costs to the UK (IE) and have been somewhat busy this last month with new wife and other changing goalposts in my life but I know already that the cost will be slightly northward of 100 pounds but this really is freight dependent.
I will make a more concrete proposal later on when I get some idea of the freight and the logistics at the UK delivery end.
Graeme